Unified paper web



Patented Sept. 26, 1939 UNIFIED PAPER WEB Richard Gurley Drew, St. Paul,Minn., assignorto Minnesota Mining 8; Manufacturing Company, St. Paul,Minn., a corporation of Delaware No Drawing.

Application March 24, 1938,

Serial No. 197,957

a Claims.

While my invention has a broad field of use-' fulness, I have found itof peculiar utility for producing an impregnating composition and forthe resultant product when applied to porous sheets for limiting theapplication of the spray of liquid finishing material such, for example,as

lacquers or paints employed in lacquering or painting operations inautomobile body paint shops and Itherefore find it convenient todescribe the invention in connection with such practice and product, itbeing understood, however, that such limited fields of specificdescription are employed purely for purposes of illustration of anexample of the utility of the invention in its several phases, besidessuch other novel fields of utility as may appear or be hereinafterpointed out.

In the work referred to specifically, my improved impregnatingcompositions may be used for treating fibrous sheets such as paperadapted to be used as the backing material of adhesive coated sheetmaterial used for holding paper aprons against surfaces on which it isdesired to apply the lacquer, paint, paint spray or lacquer spray, suchfor example as glass windows, upholstery, rubber mats of running boards,bright metal parts, and as covering and wrapping materials in general.

My invention therefore resides in the provision of sheeting materialgenerally and covering and wrapping material specifically, useful inconnection with the operations described, and the provision ofcompositions for treatment of porous sheeting materials such as paper,and to processes for producing the same.

Thecompositionsprovided by my invention may be applied to paper or othersuitable backing, particularly bibulous material, to form sheetedmaterial capable of being stacked or stored in piled sheets, or formedin laminations, as by rolling the sheets, such as in the form of rollsof tape. For certain preferred work, my compositions may be applied topaper to impart minimum point contact and inherent elasticity byapplying the same to paper which is toweled, crimped,

creped or otherwise shaped to present a surface other than fiat andwhich has extensibility beyond that of the fiat paper web.

00 Amongthe objects of my invention are the provision oi. a compositionwhich may be applied to a base, such as paper, cloth or other bibulousmaterial, providing a residuum in this base material which will resistinfiltration of paints, lacquers or the like when the base material is 5used as part of a masking adhesive sheet in painting, spraying or likeoperations; the provision of a composition for treating paper, cloth orthe like porous material resulting in a product to which an adhesivecoating maybe applied and the sheets stored in piles, stacks orlaminations without the use of slip sheeting for separating one layer ofthe composite from an adjacent layer.

My invention still further has as its object the provision of acomposition applicable to porous materials, such as paper and likesheeting material, which imparts to the paper by the residuum leftthereon, highly desirable properties, characterized by the filamentarymaterial of the paper being bonded together and rendered resistant totearing and splitting when used as a backing for an adhesive coating,more specifically, the provision of a composition which may be appliedto sheeted material comprising bibulous, uncalendered paper, toreinforce the same whereby an adherent adhesive coating may be appliedfor adhesively attaching the sheet to a surface, permitting removal ofthe composite without tearing or splitting of the paper or leaving aresiduum of the adhesive on the surface to which the composite has beenapplied.

For a clearer understanding of my invention for the production of aunified sheet, resistant to tearing or splitting, by the impregnation ofporous sheeting, my invention is predicated upon the impregnation of aporous sheet, such as porous paper, with softened or plasticizedimpregnating agents, such as proteinous materials comprising glue, andfurther resides in the discovery of the relationship of the impregnatingagent, the plasticizing material and vehicle to most effectively carryout the objectives aforesaid.

The backing materials or webs to be impregnated, as preferred by me, arepaper bases 45 which are preferably absorbent, approaching blottingpaper, calendered or uncalendered. Preferably, however, this paper baseis of the unsized, uncalendered variety and may be pressed, molded orotherwise formed to have the appearance of towelled fabric, such as bycrimping or creping the same.

Variation of the nature of the paper base such as length or quality ofthe fibersor special treat- 5 ments which increase the strength for theprocesses herein contemplated which-do not materially affect itsporosity may enhance the product or facilitate speed in production.

It is an important feature of my invention that 5 The composition of theimpregnating solution may be as follows:

Typo Glue Glycerine Water Type C above mentioned represents thepreferred procedure contemplated by me in that the backing is passedthrough a bath of the solution and thereafter passed through squeezerolls, leaving sufilcient of the saturating solution in the webultimately to leave a residuum in which the paper constitutes about 55%by weight and the residuum of glue and glycerine about 45% by weight,with the glycerine approximately 1.75 times the quantity of glue afterseparation of the water by suitable drying means.

Specifically, type A will give a thoroughly impregnated web in whichpaper constitutes 54%, glue 17% glycerine 29%.

Excellent results are obtained in carrying out the procedure under typeC by passing the web through the impregnating solution described,squeezing out the excess to the point where the web carriesapproximately twice the weight of the solution, then partially drying onracks at a temperature of from 65 to 100 F. This is followed by dippingthe web in a tanning solution of formaldehyde (4% by volume) and thenceplaced on racks where the web is dried at temperatures from to F.

The balance of the impregnating residuum to the paper, I havediscovered, may be in the range of from 52 to 60 parts by weight ofpaper to 48 to 40 parts by weight of impregnant, with the plasticizingagent in the form of glycerine, from approximately 1.7 to 2 times thequantity of glue.

In connection with types A and D above enumer ted, the impregnatingsolution will not achieve this relationship of the paper to theimpregnant and the plasticizing agent to the glue by one trip throughthe impregnating bath.

In the case of type B, the desired range of plasticizer to glue is notachieved but has utility for purposes hereinafter to be described.

To achieve the desired ratio in types A and D, the paper is firstfloated on the surface of the solution for a distance of approximatelyfour feet, then dipped into the solution of the same formula and thenpassed through squeeze rolls, where the amount of solution to be appliedis carefully regulated to give from about 24 to 2'7 parts by weight ofthe solution to 15 parts by weight of the paper.

The wet paper is then passed onto racks and into an oven where it isdried at about to F. The porosity of the treated paper may be controlledas is more specifically described in my application S. N. 29,122 filedJune 29, 1935.

Compensation is made for the higher ratio of glycerine to glue aboveindicated by then impregnating the web with a glue solution'constituting1 part glue to 2.25 to 3 parts water.

The preferred ultimate ratio as hereinabove given may be obtained byuniformly saturating the web through the expedient of the second dippingtrip. Preferably, however, the second solution is applied from one sideof the sheet, to obtain a gradient concentration from one face of thesheet to the opposite face, in the nature of a back sizing. g

After submitting the web to the second solution, the web is partiallydried on racks at temperatures of 65 to 100 F. permitting the gluepartially to\ set up and become firm. The web is then dipped into atanning solution, preferably a The ultimate products made by theemploy-- ment of the saturating solutions will be as follows:

Ratio of Type Paper Glue as glycerine to glue Percent Percent Percent Itwill be understood that in types A and D, the ratio of glycerine to gluemay be uniform from one face to the other or may represent the mean andbe gradiently proportioned from one face to the other.

Type B above specified represents a high ratio of plasticizer to glue,specifically, glycerine to glue, found desirable where this material isemployed for making adhesive-tapes of the character used for maskingtapes for spraying automobile bodies and in which the lacquer issubjected to a baking operation of from 240 to 275 F.

Where the masking tape is to be subjected to lower temperatures, typesA, C and D are preferred, in giving greater adhesive union between theadhesive layer and the backing.

Though I have described in the examples above given a tanning agent inthe nature of formaldehyde applied in the form of a solution, this maybe applied as a vapor. Also, other tanning agents, such as gallic andtannic acids, chromium trioxide, chrome alum or other chromium andaluminum salts, soluble in water, may be employed.

The tanning action may be confined to one side and has the advantage ofplacing less strain 1 on the paper than by complete submersion,particularly where the formaldehyde employed is in the form of asolution.

Neutralization of the formaldehyde, when desired, may be accomplished bysubjecting the paper to a limewater treatment.

Desirable results may be obtained in the formaldehyding treatment byretarding the action of the formaldehyde by the addition thereto ofequal molecular percentages of ammonia and this solution is used inamounts equivalent to 5% of the aldehyde to the dry weight of glue. Theformaldehyde and the retarding agent may likewise be added to theimpregnating solution just prior to the saturation or impregnating stepheretofore described, in which event during the drying of the paper, thealdehyde-ammonia content breaks down, to liberate formaldehyde, settingup, insolubilizing or tanning the glue.

While I have described glycerine as the plasticizing agent, it will beunderstood that this acts as a viscosity augmenting and water retainingpurposes.

- riety.

agent and, accordingly, other agents which fiexibilize the glue andmodify the glue may be used, with a certain amount of success, and forthis purpose there may be illustrated the following:

(1) Sulphonated castor oil;

(2) Honey (crude or refined);

The above enumerated agents may be used only in part to supplant theglycerine.

The webbing as above made may be used as a backing for adhesive tapes orfor wrapping Normally non-drying, or tacky or pressure sensitiveadhesives may be employed or .normally water-soluble or heatreactivatable adhesives may be employed.

The webbing may also be waterproofed: For the latter purposes, awaterproofing coating may be deposited upon the glue impregnated web bydipping the web in a solution of asphaltum, removing the excess on thesurface by means of pressure rolls. Coating compositions, such asparamn, Bakelite, a resinous condensation product resulting fromcondensing and resinifying a phenolic compound and an aldehydiccompound, may be used. Drying oils, such as linseed oil and varnishes,may be employed. Asphaltum, because of its flexible-qualities and lowcost may also be employed. This latter coating may be oi the tackyvariety or or the more heat resistant vacoating either of the adhesivevariety or primarily of the waterproofing variety, may be used as awaterproofing wrapping paper capable of being stacked or piled, withoutthe use of slip sheeting and is particularly tough, resilient, and

resistant to shock.

In preparing the impregnating compositions, I have described theemployment of hide glue and, in the case of type D, bone glue. Manykinds and grades of glue may be used and still produce, to a degree,desirable results, among which may be named water soluble gums, such astragacanth, and acacia. The proteinous adhesives are preferred.

In general, it. will be observed that I have provided porous webimpregnating compositions, a method of impregnating such web and aresultant unifying sheet of highly desirable properties for makingmasking tapes or wrapping materials.

Having thus described my invention and illustrated its use, what I claimas new and desire to secure by Letters Patent, is-

1. A method for the provision 01' a unified paper highly resistant tosplitting or lamination which comprises impregnating a porous web ofpaper of the character which is normally bibulous and approachingblotting paper in texture with a proteinous solution of water containinga plasticizing agent to the point where impregnation is regulated tocontain 24 to 27 parts by weight 01 the solution to 15 parts by weight01' the paper, the solution containing approximately 1 part glue, 1.75to 4 parts plasticizing agent, 3.5 to 6 parts of water, drying said webto the point where it approximately retains from 48 to 40 parts byweight of impregnant to 52 to 60 parts by weight of paper, with theplasticizing agent from 1.7 to 3 times the quantity of the proteinousagent.

2. A method for the provision oi a lmified paper highly resistant tosplitting or lamination which comprises impregnating porous paper of thecharacter which is normally bibulous and approaches blotting paper withan impregnating solution to the point where the paper retains from 48 to40 parts by weight of the impregnant residuum to 52 to 60 parts byweight of paper, the. impregnant comprising glue and glycerine in theaverage ratio of approximately 1.7 to 2 times the quantity of glycerineto the quantity of glue, distributed from one face of the web to theother the impregnant being applied diluted in water in which the watercontent is substantially not less than the combined glue glycerinecontent nor greater than approximately six times the glue content.

3. A method for the provision of a unified paper highly resistant tosplitting or lamination which comprises impregnating porous paper of thecharacter which is highly bibulous and approaches blotting paper with aglue-glycerine solution in the ratio of approximately 1 part glue, 1.75parts glycerine, 3.5 parts water, to the point where approximately 27parts of the solution are retained by approximately 15 parts by weightof paper, drying the web to the point where the ratio of paper toimpregnant residuum comprises about 56% paper to about 44% residuum,with the glycerine about 1.75 times the glue.

4. A method in accordance with claim 1 in which a solution containing atanning agent is applied to tan the glue.

5. A method in accordance with claim 2 in v terial oi the characterwhich is normally highly bibulous and approaching blotting paperimpregnated with a proteinous material and a plasticizing agent in therange of from 52 to 60 parts by weight of the web to 48 to 40 parts byweight oi! the impregnant, the plasticizing agent being present inproportions 01' about 1.7 to 3 times the quantity of the proteinousmaterial the impregnation being characterized by the effect obtained inimpregnating the proteinous material and plasticizing agent in thepresence of a water content substantially not less than the combinedproteinous material and plasticizing agent content nor greater thanapproximately six times the content or the proteinous material. 1

8. A unified paper web highly resistant to splitting or lamination whichcomprises a porous web of paper of the character which is normallybibulous and approaching blotting paper impregnated with glue andglycerine to the point constituting 52 to to parts by weight of paper to48 to 40 parts by weight 01' the combined glue-glycerine, with theglycerine aproinmately 1.7 to 2 times the quantity or glue theimpregnation being-characterized by the effect obtained in impregnatingthe glue and glycerine in the presence 01' a water content substantiallynot less than the combined glue-glycerine content, nor greater than sixtimes the glue content.

RICHARD Guam-r murw.

